Estimation of Hourly Snowmelt Discharge in a Mountainous Basin using the Distribution Function Model for the Infiltration Process of Snowmelt Water

Abstract

The present paper addresses a method for estimating the hourly snowmelt discharge mountainous catchment, using hourly data of temperature and duration of sunshine at a measuring sta situated at a low altitude.
The proposed method is applied to estimation of the hourly snowmelt discharge in the Toppu R catchment, located in the Mashike Mountains of West Hokkaido. In this study, a time series of estimated hourly snowmelt discharges were in good agreement with the observed ones.
Characteristics of the present study are summarized as follows:
(1) The method is built in the underlying physical processes from the snowmelt on the surface of snow deposit to the snowmelt through both overland and channel phases of the river. The delay time of snowmelt water passing through the snow deposit is much longer in early snowmelt season, because the snow depth is large. The present approach can estimate the snowmelt discharge at the bottom of snow deposit, using the runoff distribution function model which allows the time of concentration to vary with the depth of snow.The hourly response of a river basin to snowmelt was solved by kinematic wave routing for overland flow as well as channel flow.
(2) The peak discharge and time to the peak of the computed hydrograph compare favorably with those of the observed one for a one-month melting season.
(3) The snowmelt routine developed herein is simple to transfer spatiallydistributed snowmelt to the runoff model, which makes use of hourly air temperature at the measuring site, lapse rate and hourly radiation amount estimated from the duration of sunshine. The method is especially useful to estimate the hourly snowmelt amount in a mountainous catchment in situations where data on sites are not sufficient.
The present method is proposed as alternatives for hourly snowmelt discharge analyses.